In reversing President Obama's position on accepting corporate sponsors for this weekend's official inaugural festivities, the official inaugural committee has permitted a number of companies with interests pending before the federal government to donate.

They include such familiar blue chip names as AT&T, Microsoft and Coca Cola, but also such lesser-known companies as United Therapeutics, a biotech firm based in Silver Spring, Maryland.

United Therapeutics has in recent years been lobbying the Food and Drug Administration to grant approval of a drug the company developed to treat a lung disorder, so far without great success. In October, when an FDA ruling questioned whether the oral version of the drug did anything to slow the progress of pulmonary arterial hypertension, the company's CEO told reporters that company executives would "continue using our best efforts to gain approval [of the version of the drug] … and we will focus on doing so within the next four years."

How political contributions figure into the company's strategy is unclear. Andrew Fisher, the company's Chief Strategic Officer and Deputy General Counsel told ABC News in an email, "We're not providing any comment on this topic."

But United Therapeutics has been more aggressive than most in its support of Obama, and those contributions came at a time when the president softened his opposition to corporate money in politics. This summer, after Obama backtracked on a ban against corporate money at the Democratic National Convention in Charlotte, United Therapeutics stepped up.

The biotech company was the sixth largest corporate donor to the administrative arm of the convention host committee, called New American City, Inc., only finishing behind such financial giants as Bank of America, AT&T and Duke Energy. The company gave $600,000, according to contribution records.

The company's CEO has also been a major donor to the Democratic Party, and to Obama's campaign, giving more than $125,000 in the past four years.

Sheila Krumholz, executive director of the Center for Responsive Politics, which advocates for transparency in the way politics is financed, said the decision to allow corporate money is just one of several changes in the way Obama has approached financing inaugural events. Gone also are self-imposed caps on the amounts that individuals can donate. And, Krumholz said, the inaugural committee has back-tracked on the level of transparency displayed in 2009, when Obama was first sworn into office.

"This inauguration and, particularly the funding of it, stands in stark contrast to the previous inauguration," she said.

The changes are consistent with a subtle shift in the way Obama has handled touchstone issues surrounding money and politics. Obama was once a critic, for instance, of the so-called Super PACs that were established to raise unlimited funds to support campaigns. But in his 2012 reelection bid, Obama advisors set up an organization, Priorities USA, for just that purpose.

Krumholz said she believes corporate donors, in particular, warrant scrutiny.

"I think that with all these corporations, they are giving because they see that contributions to the inauguration, to the convention, to the campaigns, to all these different pots of money might be beneficial to their corporation and to their legislative policy agenda in Washington," Krumholz said. "It's not natural for a corporation, which has to uphold and protect its bottom line, to be making contributions out of altruistic reasons or to support democracy. They have reasons which I think bear scrutiny."

Krumholz's group researched the backgrounds of the corporate donors and found that more than 300 registered lobbyists worked on behalf of five large corporate donors to the inauguration -- AT&T Inc., Microsoft Corp., energy giant Southern Co., biotechnology firm Genentech and health plan manager Centene Corp. -- to influence legislation and government policy.

Parties other than the official inaugural balls are not covered by this money. Dozens of other parties have private sponsorship.

The Presidential Inaugural Committee has published the names of all of its donors on its web site, though Krumholz notes that the list does not include basic identifying information, such as the donor's employer or address, and it does not say how much money any donor has given.

The list includes a number of the president's close friends and longtime supporters, as well as familiar Democratic Party patrons, including a number of labor unions.

The American Federation of Government Employees, the American Postal Workers Union, the International Association of Firefighters, the International Brotherhood of Electrical Workers, the International Union of Painters and Allied Trades, the Laborer's Union, the Sheet Metal Workers International Association, and the United Food & Commercial Workers, all ponied up with support.

A document identifying the rewards for major donors, first reported by The New York Times, spells out how those who provide the most money will have had greater access this weekend. Individuals in the top package who gave $250,000 and institutional donors who gave $1 million are identified as "Washington" donors, (as opposed to "Adams" or "Jefferson" donors, who gave less) are entitled to such perks as tickets to the "Co-Chairs Reception," entry to the "Road Ahead" meeting for the president's top supporters, "VIP tickets to the Candle Light Celebration at the National Building Museum" and two reserved bleacher seats for the Inaugural Parade.

Efforts to reach the inaugural committee this weekend have been unsuccessful. According to the Sunlight Foundation, which has also been tracking money at the inaugural festivities, officials with the Presidential Inaugural Committee have been tight-lipped about the details of the finance effort. They quoted Brent Colburn, communications director for the 2013 Presidential Inaugural Committee as telling reporters that the committee, by listing donors on its website has attempted "to go above and beyond that and add a level of transparency."

In December 2012, when ABC News first reported Obama's position switch on corporate donations, a spokesperson for the inaugural committee said all donors would be vetted and that donations from lobbyists or political action committees (PACs) will not be accepted.

"Our goal is to make sure that we will meet fundraising requirements for this civic event after the most expensive presidential campaign in history," spokesperson Addie Whisenant said then.